A field trial was conducted in 2025 at the Oxford Research Station in Oxford, Nc, to evaluate fungicide and adjuvant programs for managing target spot in tobacco. The study was set up using a randomized complete block design with four replications to ensure reliable results. Each plot was 14.7 feet wide and 50 feet long, containing two rows of tobacco, with one treated row used for evaluation. The tobacco variety 'K326' was transplanted on 5/8/2025 using a mechanical tobacco transplanter, following standard non-irrigated tobacco production practices in North Carolina. The field was inoculated with 2 strains of Rhizoctonia solani AG3 mycelia 2 weeks after transplant.
The trial compared 14 different fungicide treatments against an untreated control. Each treatment included three applications throughout the season (Table 1):
- First application: June 11 (4 weeks after transplanting - layby)
- Second application: June 25 (6 weeks after transplanting)
- Third application: July 9 (8 weeks after transplanting)
Fungicides were applied using a CO₂-pressurized backpack sprayer, ensuring proper coverage and accurate application rates. Target spot severity was monitored by evaluating five plants per plot at different stalk positions:
- Lower stalk (lugs)
- Middle and upper-middle stalk (cutters and leaf)
- Upper stalk (tips)
These assessments were conducted biweekly from May through July to track disease progression. The results were summarized using the Area Under the Disease Progress Curve (AUDPC), a common method for measuring disease severity over time. Four harvests were conducted at the end of the season.
The season conditions were average, and disease peaked around ten weeks after transplant at about 8% on the lower stalk.
There was a significant reduction in disease severity in the following rotations compared to the check (Figure 1):
- Excalia followed by Excalia followed by Quadris Flowable
- Excalia followed by Quadris Flowable followed by Excalia
